Making sugarcane, sorghum into oil-producing crops

Diana Yates, University of Illinois

Mon, 2012-03-12 14:51

Researchers aim to boost the natural, oil-producing capabilities of sugarcane and sorghum, increase the crops’ photosynthetic power and – in the case of sugarcane – enhance the plant’s cold tolerance so that it can grow in more northerly climes.

With the support of a $3.2 million grant from the U.S. Department of Energy, researchers will take the first steps toward engineering two new oil-rich crops. They aim to boost the natural, oil-producing capabilities of sugarcane and sorghum, increase the crops’ photosynthetic power and – in the case of sugarcane – enhance the plant’s cold tolerance so that it can grow in more northerly climes.

The initiative, led by researchers at the University of Illinois in collaboration with scientists at the University of Florida, the University of Nebraska and the Brookhaven National Laboratory, will make use of recent advances in plant biotechnology and computer modeling to produce high-yielding, cold-tolerant, photosynthetically efficient crops that can be used in the production of biodiesel and jet fuel.

“Plants already have all the genetic apparatus to make oils,” said Illinois crop sciences and Institute for Genomic Biology professor Stephen Long, who leads the initiative. “It’s in their genomes.”

Once they have matured, sugarcane and sorghum spend much of their energy making and storing sugars, he said.

“We are proposing to subvert that mechanism in the plant to, instead of making sugar, use the products of photosynthesis to make oils and deposit those in the stems.”

These natural plant oils, known as triacylglycerols, can be converted into diesel and jet fuel by a chemical process known as hydro-treatment.

“Ethanol is somewhat problematic in that we don’t have any pipelines for distributing it around the country,” Long said. “And we have to deal with the blend-wall – that is, most current cars cannot deal with more than 10 percent ethanol, setting a limit on the amount of gasoline we can replace at present.”

Traditional oil-producing plants, such as soybeans, can’t produce enough oil per unit of land to make this approach cost effective in the long-term without subsidies, Long said. But sugarcane and sorghum, which are among the most productive plants in agriculture, could feasibly produce more than 10 times the amount of oil per acre of crops such as canola and soybean, Long said.

The new work will build on previous studies that have identified genes that enhance oil production in plants and genes that boost their photosynthetic efficiency.

Long and his colleagues also will make use of their knowledge of Miscanthus x giganteus, a perennial grass already used as a biofuels feedstock. The use of this new crop was first pioneered in the U.S. at the U. of I. Miscanthus can grow up to 13 feet (3.9 meters) tall and is closely related to sugarcane but is much more tolerant of cold weather. The researchers hope to introduce the genes that enhance its cold tolerance into sugarcane, which today can survive only in the hottest parts of southern U.S. states.

Another project will look at engineering bacteria to produce diesel directly and, once the process is streamlined in the bacterium, transfer the critical genes to sugarcane and sorghum.

“Sorghum and sugarcane will grow on quite poor land, so this should be doable without competing with food-crop production,” Long said. “The amount (of oil) we can get per unit (of) land area really makes this economically very viable as well, so I think it has the potential to give significant energy security to the country.”

Long said he expects to have early “proof of concept” results within 18 months.